1. Field of the Invention
The invention relates to metering devices or other lubricant transfer devices that rely on a negative pressure to remove lubricant from a source. More particularly, the invention relates to an adapter permitting the use of a standard lubricant storage cartridge in a lubricant dispenser of such a lubricant transfer device. The invention also relates to an improved method of mounting a replaceable lubricant storage cartridge on a lubricant transfer device and of replacing the thus-mounted storage cartridge.
2. Discussion of the Related Art
A variety of systems employ a transfer device which draws lubricant from a source using a negative pressure, i.e., at least a partial vacuum. The transferred lubricant may comprise grease, oil, or any other liquid or semi-liquid lubricant. A common example of such a transfer device is a lubricant metering device.
Lubricant metering devices are well-known for the precision feeding of lubricant to downstream equipment for lubrication purposes. The typical metering device includes, inter alia, a source and a lubricant metering pump that receives lubricant from the source and that pumps the lubricant to an outlet of the metering device for transfer to downstream equipment. The typical metering pump includes a reciprocating piston that passes through a supply chamber and into a metering chamber. Lubricant is drawn into the supply chamber from the source by way of a negative pressure or partial vacuum generated upon piston movement. A metering device of this general type is disclosed, for example, in co-pending U.S. patent application Ser. No. 08/987,595 (the '595 application), Lukas et al., filed on Dec. 9, 1997, now U.S. Pat. No. 5,876,189, issued Mar. 2, 1999, and assigned to a common assignee, the subject matter of which is hereby incorporated by reference.
The lubricant source for the typical lubricant metering device comprises either 1) a permanent reservoir or 2) a rather complex assembly of a housing and a reciprocating piston. Permanent reservoir-type containers must be periodically filled using a grease gun or the like at substantial operator inconvenience and risk of spills. Housing assemblies can be filled more easily, but must be at least partially disassembled in a time consuming task that itself risks spills.
Replaceable lubricant storage cartridges are well known in other lubricant dispensing applications. The typical storage cartridge of this type is designed for use with a grease gun or some other device that employs a mechanically-driven piston to force the lubricant out of the storage cartridge. Storage cartridges of this type are disclosed, for example, in U.S. Pat. No. 3,121,516 to Dewees et al. (Dewees) and U.S. Pat. No. 4,869,403 to Bruning (Bruning).
Unfortunately, the storage cartridges disclosed in the Dewees patent and the Bruning patent as well as other, similar storage cartridges are incompatible for use with conventional metering devices for several reasons. For instance, a typical grease gun forces grease out of one end of the storage cartridge by mechanically driving a piston through the storage cartridge from the opposite end. The grease gun therefore is designed for attachment to the storage cartridge primarily at the storage cartridge's opposite end. The typical metering device cannot receive a storage cartridge in this manner. Moreover, the typical arrangement for attaching a storage cartridge to a grease gun does not need to form an air-tight seal at the interface between the storage cartridge and the grease gun because dispensing occurs under mechanical pressure rather than under a partial vacuum or negative air pressure.
The need has therefore arisen to adapt a standard lubricant storage cartridge for use with a lubricant metering device or the like.